This invention relates to electrically powered smoking articles, and particularly to methods and apparatus for controlling the supply of energy to electrically powered smoking articles.
A smoking article is a device in which a flavor generating material, such as tobacco or a tobacco-derived substance, is heated in order to release flavorants. One type of smoking article is described in commonly assigned U.S. Pat. No. 5,060,671, which is hereby incorporated by reference in its entirety. That patent describes an electrically heated smoking article that uses a disposable array of electrical heating elements. Each heating element has an individual charge of tobacco flavor generating material deposited thereon. The disposable array is easily mated to the "permanent" portion of the smoking article, which contains a power supply, such as a battery, and control circuitry. In such a device, an aerosol or vapor containing flavorants is generated as a result of a transfer of thermal energy from at least one, but less than all of the heating elements to the tobacco flavor generating material deposited thereon for each puff taken by the smoker.
In smoking articles which use an array of heating elements, control circuitry should be provided for selecting which of the heating elements in the array will be energized for a particular puff. If the smoker is required to manually select the particular element to be heated, the enjoyment associated with using a smoking article may be diminished. Furthermore, the control circuitry should be capable of preventing repeated actuation of any one heating element, to avoid re-heating of a charge of tobacco flavor generating material and consequent generation of undesirable compounds which may have an adverse impact on flavor.
The control circuitry in a smoking article should also be capable of regulating the power delivered to each heating element to ensure that a sufficient amount of energy is transferred to the tobacco flavor generating material, so that a consistent aerosol or vapor is generated for each puff. The power source of such smoking articles (typically a battery or a series of batteries) loses charge over time; therefore, it may be necessary to energize the heating elements longer as the power supply ages, in order to deliver the same amount of energy as when the power supply was new, so as to achieve an acceptable aerosol or vapor.
Smoking articles are typically small, handheld devices that are carried by the smoker, and the power supply in such devices (i.e., the batteries) have limited storage capacity. Thus, the control circuitry for an electrically powered smoking article should not excessively consume the limited power resources. Furthermore, the control circuitry should be capable of informing the smoker when the power supply is no longer able to deliver enough energy fast enough during a puff to provide an acceptable aerosol or vapor.
In view of the foregoing, it would be desirable to provide a method and an apparatus for controlling the delivery of energy to a heater array in a smoking article so that a predetermined amount of energy is delivered to individual heating elements in the heater array on demand.
It would also be desirable to provide a method and an apparatus for controlling the delivery of energy to a heater array in a smoking article which minimize the amount of energy required to control the heater array.
It would further be desirable to provide a method and an apparatus for controlling a heater array in a smoking article so that energy is automatically and sequentially delivered to unused heating elements on demand until all of the heating elements in the heater array have been powered.
It would still further be desirable to provide a method and an apparatus for controlling a heater array which automatically detect the presence of the heater array.
It would yet further be desirable to provide a method and an apparatus for controlling a heater array which notify the smoker when the power supply has discharged to an unacceptable level.